Work vehicles, such as those used in the agricultural, construction and forestry industries, often have work implement attachments, such as buckets, rippers, scrapers and the like, used for operations such as grading, excavating, tilling, and general site preparation. Conventional work vehicles are equipped with some type of operator control, for example, various hand controls, switches, levers and joysticks for controlling the movements of these implements. The operator uses such controls to control the movements of the implements. For example, in the case of a ripper attachment, the operator can control the height and pitch of the ripper, and for a scraper, the scraper bowl opening, the ejector position, and the depth of the scraper blade.
The off-road environments often encountered by such work vehicles can be extremely rough, especially in tracked vehicles, thus making the operation of the attachment component difficult for the vehicle operator. The operator is often required to make fine adjustments in the positioning of the controls in order to accurately articulate the associated implement, all while being shaken or jostled about within the cab. Fine adjustments can be particularly difficult without sufficient hand support. Moreover, conventional multi-function controls require the operator to be able to manipulate numerous switches or buttons while positioning the control.
Some work vehicles, for example, use a dual-axis joystick to control the various movements of the work implement. However, conventional dual-axis joysticks generally do not stabilize the operator when operating the work vehicle in rough conditions. This can lead to unstable operator positioning as well as unintended movement of the joystick. Other conventional controls for work implements include multiple switches that are difficult to reach or manipulate simultaneously, and thus these controls suffer from similar shortcomings in control functionality and operator stability, particularly in rough operating conditions.
U.S. Pat. No. 5,768,947 discloses one example of an operator control device for use in an off-road vehicle. In particular, this patent discloses an operator control device for a tracked vehicle having a ripper attachment. The device provides a hand support in the form of an upwardly canted cantilevered hand grip. At the end of the hand grip is a rotatable thumb lever. The thumb lever is mounted to a rotating shaft running through the core of the hand grip, which interacts with one or more position sensors inside the device. The sensors cooperate with other control electronics to, linearly and non-linearly, control the ripper hydraulic control valve(s) necessary to control the vertical position of the ripper. One significant disadvantage of the disclosed control device is that to control the ripper pitch (i.e., the fore and aft movement of the ripper teeth), the operator must manipulate a second lever mounted to the base of the device, off of the hand grip itself. Thus, in order to fully control the implement, the operator must manipulate both, at times simultaneously, both a hand grip mounted switch and a base mounted switch. Moreover, the pitch adjustment is another rotational input, which given the location and switch mechanism disclosed, may require the operator to use two fingers, such as index and middle fingers, to maneuver the ripper teeth in the desired fore and aft position. The extra digits required to manipulate the controls diminishes the operator's grip on the hand grip, which can cause operator instability and compromise control precision.